I don't even think narcan would do anything for a fentanyl overdose that could be life threatening.
This is a harm reduction site, it IS good that people are incredibly cautious, but, fentanyl gets some kind of special attention simply because it is so potent. What you have is pharm grade 50mcg intranasal fentanyl and even with your low tolerance, 1 shot shouldn't cause a problem.
Honestly, I would suggest 2 if I knew that you were in a safe setting (like a hospital) but I don't. If the OP meant that 6mg of hydromorphone is manageable as an oral dose, I would certainly say that starting with 1 shot up the nose without other drugs active should cause a nice sedation. Don't be too freaked out, fentanyl makes even seasoned opiate users puke for their first time. Be careful. Good luck.